On 26 September 2022 humans made our first measurable change to a Solar System object, as NASA’s DART spacecraft impacted the Dimorphos asteroid, shifting its orbit around its larger Didymos parent asteroid.
This grand experiment was a success, but many unknowns remain, to be investigated by ESA’s Hera mission in close-up. What is the precise mass and structure of Dimorphos? Why was it deflected so much more than previous simulations forecast? How did the impact change the Great-Pyramid-sized asteroid? Has it been left with a giant crater, sent spinning wildly or perhaps reshaped entirely?
Finding out will help make the ‘kinetic impactor’ method of planetary defence into a well-understood technique that could be deployed reliably if we ever need it for real.
Launch: 7 October 2024
Target: Asteroid Dimorphos
Rendezvous: November 2026
151 m
target asteroid
1 st
binary asteroid survey
12
mission payloads
2
CubeSats
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Orbital inclination of asteroid Didymos
Orbital inclination of asteroid Didymos
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OSIRIS-REx PI endorses Hera
The Principal Investigator of NASA's asteroid sample return mission has issued a letter of support for Hera
Planetary Society endorses Hera
The Planetary Society urges ESA's Member States to fund the Hera mission
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Hera mission overview
Hera – named after the Greek goddess of marriage – launched on 7 October 2024 and is travelling to the Didymos binary asteroid system.The 780 m-diameter, mountain-sized main body, Didymos, is orbited by a 151 m moon, Dimorphos, about the same size as the Great Pyramid of Giza.Dimorphos is historically significant as the first object in the Solar System to have its orbit shifted by human effort in a measurable way, when NASA's Double Asteroid Redirection Test, or DART, collided with the asteroid on 26 September 2022.Hera's detailed post-impact survey of the asteroids in 2026/2027 will turn this grand-scale kinetic impact experiment into a well-understood and repeatable technique for defending Earth from potentially hazardous asteroids.
Didymos and Dimorphos
The target of ESA's Hera mission is asteroid (65803) Didymos (1996 GT), an Apollo-type rocky (S-type) near-Earth object (NEO) with a perihelion (minimum distance to the Sun) that is just below the aphelion radius (maximum distance to the Sun) of Earth orbit.
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ESA's first planetary defence mission
First light: Hera resolves two asteroids instead of one
The European Space Agency’s Hera spacecraft for planetary defence has resolved its two target asteroids separately for the very first time, revealing the binary nature of the Didymos system, currently some 197 million km away from Earth.
Braking news! Time for ESA’s Hera asteroid mission to go slow
Launched two years ago today, the European Space Agency’s Hera mission for planetary defence has been hurtling away from Earth ever since. The small-car-sized spacecraft is now preparing for its single most challenging activity since lift-off: the sustained braking manoeuvres to slow it down to approach its target asteroids.